Power converter responsive to device connection status

ABSTRACT

Various embodiments of apparatuses, systems, and methods for controlling the operating status of a power converter during, a standby mode, a powered mode, and a transition from the standby mode to the powered mode is described. For at least one embodiment, a power converter includes a primary controller and a secondary controller wherein the primary controller includes a first circuit configured to initiate a transition from standby mode to powered mode upon receipt of a wake-up signal and wherein the first circuit is powered during standby mode.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority to U.S. Utility patentapplication Ser. No. 15/705,389, filed on Sep. 15, 2017, in the name ofinventors BongGuen Chung et. al., and entitled “Power ConverterResponsive to Device Connection Status,” the entire contents of whichare incorporated herein by reference.

TECHNICAL FIELD

The technology described herein generally relates methods, systems, andapparatus for controlling currents and voltages produced by powerconverters. The technology described herein also relates to methods,systems, and apparatus for controlling currents and voltages produced byswitch mode operated power converters. More specifically, the technologydescribed herein relates to methods, systems, and apparatus forcontrolling voltages and currents, using switch mode power converters,during standby periods and when power is not needed to awaken a powerconverter to power a device. The technology may find use in conjunctionwith various electronic devices, such as power converters configured foruse with personal communications devices, such as mobile phones andtablets, and with other devices which have varying load needs and whoseneeds for voltages and currents vary over time.

BACKGROUND

Today, power converters are commonly used in conjunction with variousdevices such as mobile phones, tablets, computers, and other adaptiveand non-adaptive devices (hereafter, each an “adaptive device”) toconvert line voltages, such as the U.S. standard 120 volts AC, intovarious output voltages and currents (hereafter, each a “load request”)then desired by an adaptive device. Power converters commonly operate inat least two modes, powered mode and standby mode. During powered mode,power converters commonly convert input voltages and currents, such asthose provided from an electrical circuit provided in a house, businessor otherwise (an “input power”), into the voltages and currentsrequested by an adaptive device (a “load”). However, while powerconverters often remain connected to a source, adaptive devices are notalways connected to or acting as a load to the power converter—suchnon-connected/non-load mode of operation for a power converter beingreferred to herein as “standby mode.” While in standby mode, powerconverters today typically continue to draw power from the source andconvert such input power into low-level voltages and currents needed bythe power converter itself to remain responsive to a later arising load.

While the continual powering of a power converter during standby modeenables the power converter to be highly responsive to load requests, itwastes energy. In some existing implementations, as much as 20-30milliwatts of power is wasted during standby mode (hereafter, “standbypower”). Over extended periods of time and in view of the millions ofpower converters in present use today, such power losses from standbypower can be substantial.

One type of power converter commonly used today is a switch mode powersupply. Switch mode power supplies commonly include a transformer havinga first (primary) coil, a second (secondary) coil, and a third (sensing)coil. The primary coil is commonly connected to the input power sourceand the secondary coil is commonly connected to the adaptive device.During power mode, the primary coil, secondary coil, and sensing coiloperate per design and often efficiently convert input power into thedesired load. During standby mode, however, the primary coil connectedto the input power source typically operates to maintain an outputvoltage at a constant voltage (such as 5 volts) although no load isconnected. This providing of the 5 volts to the secondary coil enablesthe power converter to respond quickly to load demands But, as discussedabove, this approach wastes power.

While it is appreciated that a primary coil can be powered down byopening a circuit between the primary coil and the input power source,it is to be appreciated that such an approach often involves humanintervention to reactivate the primary coil. That is, per such anapproach, the connecting of an adaptive device (or the generation of anew load request from an already connected adaptive device) commonlyrequires human intervention to power on the primary coil as no knownmechanism exists today for automatically activating a primary coil of apowered down power converter.

Accordingly, a power converter is needed that has a primary coil thatcan be powered down during standby mode and thereby not waste power,but, can be automatically awakened and responsive to new load requests,as needed.

The various embodiments of the present disclosure address the above andother concerns by providing for highly sophisticated control of standbymode of power converters and, in particular, switch mode powerconverters, by providing a secondary side control circuit that iscapable of receiving a new load request from a connected adaptivedevice, and is configured to respond to such new load request byactivating a primary side of the power converter without humanintervention.

SUMMARY

In accordance with at least one embodiment of the present disclosure anapparatus, system, or method for minimizing power consumed by a primaryside of a power converter during standby mode and, in response to a newload request, automatically enabling powered mode of operation isprovided.

In accordance with at least one embodiment of the present disclosure, apower converter comprises a primary controller configured to control theoperating status of a first coil of a transformer during a standby mode,a powered mode, and a transition from the standby mode to the poweredmode. For at least one embodiment, the primary controller may furthercomprise a primary switch controller and driver circuit, a first circuitconfigured to initiate transition of the primary switch controller anddriver circuit from the standby mode to the powered mode upon receipt ofa wake-up signal, wherein the first circuit is a first wake-up circuitthat is powered during standby mode. A secondary controller,electrically connected to a second coil of the transformer, may beincluded in the power converter and further comprise a second circuitconfigured to detect a connecting of a device to the power converter.

For at least one embodiment, the second circuit may be a secondarywake-up circuit and the secondary controller may be powered by thedevice during the transition from the standby mode to the powered mode.The secondary controller may be configured to output the wake-up signalwhen the device is connected to the power converter. The primary switchcontroller and driver circuit are not powered during standby mode.

For at least one embodiment, the power converter may include anopto-coupler configured to transmit the wake-up signal from thesecondary controller to the primary controller.

For at least one embodiment, the secondary wake-up circuit may beconfigured to detect the connecting of the device to the secondarycontroller upon receipt of a device wake-up signal.

For at least one embodiment, the secondary wake-up circuit may beconfigured to monitor voltage potentials formed across a voltage dividercircuit to detect when the device is electrically connected to the powerconverter. The power converter provides a first resistive element of thevoltage divider circuit. The device provides a second resistive elementof the voltage divider circuit. A voltage divider circuit is formed whenthe device is electrically connected to the power converter. A firstvoltage potential is formed when the power converter is not electricallyconnected to the device. A second voltage potential is formed when thepower converter is electrically connected to the device.

For at least one embodiment, the secondary controller is configured foruse with an electrical circuit formed with the device. For at least oneembodiment, the electrical circuit includes a detecting circuitconfigured to detect the formation of an electrical connection betweenthe device and the power converter. For at least one embodiment, theelectrical circuit includes and a signaling circuit configured tooperate a device switch, wherein upon closure of the device switch adevice battery provides electrical power to the secondary controller.For at least one embodiment, at least one of the detecting circuit andthe signaling circuit are provided by the device

For at least one embodiment, during standby mode the primary switchcontroller and driver circuit control the operation of a primary switchconnected to the first coil to maintain a no-load output voltage.

For at least one embodiment, the secondary controller comprises acompensator circuit configured to control output ripples generated bythe second coil.

For at least one embodiment, a compensator comprises an amplifierconfigured to compare a reference voltage signal with a thresholdvoltage and output a compared reference voltage signal, wherein thereference voltage signal represents the output voltage of the powerconverter, and the threshold voltage is predetermined. For at least oneembodiment, a compensator comprises a variable resistor, electricallyconnected to the amplifier, and configured to adjust the adjust thevoltage of the compared reference voltage signal. For at least oneembodiment, when a device is connected to the second controller, thecompensator outputs a first feedback signal, and when a device is notconnected to the second controller, the compensator outputs a secondfeedback signal. For at least one embodiment, the second circuitcomprises an attachment detector configured to decrease the resistanceof the variable resistor when the device is attached to the powerconverter and to increase the resistance of the variable resistor whenthe device is detached from the power converter.

For at least one embodiment, a power converter comprises a primarycontroller configured to control the operating status of a first coil ofa transformer during a standby mode, a powered mode, and a transitionfrom the standby mode to the powered mode. For at least one embodiment,the primary controller comprises a primary switch controller and drivercircuit. For at least one embodiment, the primary switch controller anddriver circuit are not powered during standby mode. For at least oneembodiment, the primary controller comprises a primary powered coilwake-up circuit configured to initiate transition of the primarycontroller from the standby mode to the powered mode upon detection of aprimary voltage signal induced in a third coil of the transformer. Forat least one embodiment, the primary voltage signal is induced in thethird coil of the transformer upon the powering of the second coil by adevice electrically connected to the second coil.

For at least one embodiment, a power converter comprises a secondarycontroller, electrically connected to a second coil of the transformer,and configured to control the powering of the second coil during standbymode. For at least one embodiment, the secondary controller comprises asecondary wake-up circuit configured to detect a connecting of thedevice to the power converter and a secondary switch controllerconfigured to control a duty cycle of a second switch electricallyconnected to the second coil. For at least one embodiment, the secondaryswitch controller closes the second switch upon detection by thesecondary wake-up circuit of the connection of the device to the powerconverter. For at least one embodiment, a device battery powers thesecond coil during the transition from standby mode to powered mode.

For at least one embodiment, a secondary wake-up circuit is configuredto detect the connecting of the device to the power converter bymonitoring voltage potentials formed across a voltage divider circuit.For at least one embodiment, the power converter provides a firstresistive element of the voltage divider circuit and the device providesa second resistive element of the voltage divider circuit. For at leastone embodiment, the voltage divider circuit is formed when the device iselectrically connected to the power converter such that a first voltagepotential is formed when the power converter is not electricallyconnected to the device and a second voltage potential is formed whenthe power converter is electrically connected to the device.

For at least one embodiment, the secondary controller is configured foruse with an electrical circuit formed with the device. For at least oneembodiment, the electrical circuit includes a detecting circuitconfigured to detect the formation of an electrical connection betweenthe device and the power converter. For at least one embodiment, theelectrical circuit includes a signaling circuit configured to operate adevice switch, wherein upon closure of the device switch a devicebattery provides electrical power to the secondary controller. For atleast one embodiment, at least one of the detecting circuit and thesignaling circuit are provided by the device.

For at least one embodiment of the present disclosure, a primarycontroller for use with a power converter comprises an IMIN controllerconfigured to control currents output by a power converter duringstandby mode, powered mode, and transitions from the standby mode to thepowered mode.

For at least one embodiment, an IMIN controller comprises a low voltagedominant bypass circuit configured to compare the currents provided in afeedback signal against a peak current threshold and output the lesserof the compared signals.

For at least one embodiment, an IMIN controller comprises a high voltagedominant bypass circuit configured to second compare the output of thelow voltage dominant bypass circuit with a selected output current leveland output the higher of the second compared signals.

For at least one embodiment, an IMIN controller comprises a selectorconfigured to detect an electrical connection of a device to the powerconverter. For at least one embodiment, the connection is detected basedupon a rapid variation in the feedback signal or the primary voltagesignal in a third coil of the transformer. For at least one embodiment,an IMIN controller comprises a selector configured to select between afirst IMIN level and a second IMIN level. For at least one embodiment,the first IMIN level is less than the second IMIN level. For at leastone embodiment, the selector selects the first IMIN level when a deviceis electrically connected to the power converter. For at least oneembodiment, the selector selects the second IMIN level when a device isnot electrically connected to the power converter.

BRIEF DESCRIPTION OF THE DRAWINGS

The features, aspects, advantages, functions, modules and components ofthe apparatus, systems and methods provided by the various embodimentsof the present disclosure are further disclosed herein regarding atleast one of the following descriptions and accompanying drawingfigures.

FIG. 1 is schematic representation of an electrical circuit forcontrolling the awakening of a power converter from standby mode topowered mode in accordance with a first embodiment of the presentdisclosure.

FIG. 2 is a flow chart representation of a method for awakening a powerconverter from standby mode to powered mode in accordance with the firstembodiment of the present disclosure.

FIG. 3 is a schematic representation of an electrical circuit forcontrolling the awakening of a power converter from standby mode topowered mode in accordance with a second embodiment of the presentdisclosure.

FIG. 4 is a flow chart representation of a method for awakening a powerconverter from standby mode to powered mode in accordance with thesecond embodiment of the present disclosure.

FIG. 5 is a schematic representation of an electrical circuit forcontrolling the awakening of a power converter from standby mode topowered mode in accordance with a third embodiment of the presentdisclosure.

FIG. 6 is a schematic representation of an electrical circuit forcontrolling the awakening of a power converter from standby mode topowered mode in accordance with a fourth embodiment of the presentdisclosure.

FIG. 7 is a schematic representation of an electrical circuit forcontrolling the awakening of a power converter from standby mode topowered mode in accordance with a fifth embodiment of the presentdisclosure.

FIG. 8 is a schematic representation of a primary current controlcircuit for use in determining the mode of operation of a powercontroller in conjunction with at least one embodiment of the presentdisclosure.

FIGS. 9A-9B are timing diagrams illustrating representative voltages andcurrents detected by a primary current control circuit for respectivehum and hum settings in accordance with at least one embodiment of thepresent disclosure.

DETAILED DESCRIPTION

The various embodiments described herein are directed to apparatus,systems, and methods for controlling standby power and transitioning toa power mode of operation in power converters. More specifically, theembodiments described herein are directed to methods, systems, andapparatus for controlling transitions between standby and power modes inswitch mode operated power converters. The embodiments described hereinmay find use in electronic devices, such as power converters configuredfor use with personal communications devices, such as mobile phones andtablets, and with other devices whose requests for voltages and currentsprovided by a power converter vary over time including periods of timewhen the device is either not connected to the power converter or a loadrequest is not then pending. While the various embodiments set forthherein, and as shown in the attached drawing figures, provide sufficientinformation for a person of ordinary skill in the art to practice one ormore of the inventions, as claimed herein or as later claimed in anyapplication claiming priority to this disclosure, it is to beappreciated that one or more embodiments may be practiced without one ormore of the details provided herein. As such, the various embodimentsdescribed herein are provided by way of example and are not intended andshould not be used to limit the scope of any invention claimed to anyembodiment.

As shown in FIG. 1 and for at least one embodiment of the presentdisclosure, a power converter 100 having a primary side and a secondaryside is provided. The power converter 100 may be configured to include atransformer 101 having a first coil L1, a second coil L2 and a thirdcoil L3. The first coil L1 and third coil L3 being located on theprimary side of the power converter 100 and of the transformer 101. Thesecond coil L2 being located on the secondary side of the powerconverter 100 and transformer 101.

Primary Side of Power Converter

First Coil:

The first coil L1 includes a first terminal T1 suitably connected to afirst primary port PP1 which, in at least one embodiment, functions as aprimary input power port configured to receive input voltages andcurrents from a power source (not shown). The power source may be analternating current (AC) source whose input signal is suitably rectifiedinto a direct current (DC) source, a DC power source, or otherwise.Input power signal conditioning may be provided using capacitors C1 andC2 and resistor R2 which are connected in parallel to the first terminalT1. Power converter 100 may include diode D1 which is connected to asecond terminal T2 of the first coil L1 and configured to preventreverse biasing of first coil L1. Resistor R1 may also be provided andis connected to the first terminal T1 to provide a primary controller102, via a second primary port PP2, with a primary input voltage signalS_(V) which is a representation of the input voltages provided by thepower source to the first coil L1. The components, connectivity andsignals used by the primary controller 102 are discussed in greaterdetail below.

First Switch:

A first switch S1 is connected to the second terminal T2 of the firstcoil L1. In at least one embodiment, the first switch S1 is a MOSFETwith the drain being connected to the second terminal T2. It is to beappreciated that in other embodiments, other configurations and orarrangements of switching components, including MOSFETS or otherwise,may be utilized as desired for any implementation. A diode D2 representsthe body diode of MOSFET S1.

The gate of the first switch S1 is connected to a third primary port PP3of the primary controller 102. The primary controller 102 is configuredto output, via the third primary port PP3, the primary gate controlsignal S_(PG). S_(PG) controls the duration (pulse width) and frequencyduring which the first switch S1 is “on” and “off.” A primary currentI_(P) is generated through the first coil L1 during each turn-on periodof S1.

The source of the first switch S1 is connected to a resistor R3 which isalso connected to ground. When the first switch S1 is “on”, the currentsensing voltage signal S_(PV) is generated and represents the voltageacross the resistor R3. When the first switch is “on,” a primary currentI_(P) flows from the power source and through the first coil L1, thefirst switch S1 and resistor R3 to ground. The current sensing voltagesignal S_(PV) is provided to the primary controller 102 via a sixthprimary port PP6.

Third Coil:

The power converter 100 and transformer 101 also includes a third coilL3. The third coil L3 includes a third terminal T3 and a fourth terminalT4 which is grounded. The third terminal T3 is connected to the primarycontroller 102 via diode D4 and the fourth primary port PP4. The thirdterminal T3 is also connected to the primary controller 102 via a firstvoltage divider circuit formed by resistors R4 and R5 and the fifthprimary port PP5. The third coil L3 provides to the primary controller102 two signals representative of the voltages and currents transferredby the first coil L1, as represented by voltages and currents generatedin the third coil L3, during each duty cycle of the power converter 100.More specifically, the third coil L3 generates and provides an appliedvoltage signal S_(VDD) to the primary controller 102 via the fourthprimary port PP4. S_(VDD) is generated by the third coil L3 andrepresents the voltages and currents generated by the transformer 101over each duty cycle. Second, the third coil L3 generates and provides ascaled primary voltage signal S_(PVS) to the primary controller via thefifth primary port PP5 over each duty cycle. S_(PVS) is a scaledrepresentation of the voltage across the third coil L3 proportional tothe voltage across the second coil L2. Diode D4 and capacitors C3 and C4provide rectifying and filtering for the S_(VDD) and S_(PVS) signals.

Opto-Coupler:

The power converter 100 also includes an opto-coupler 108 a-b whichincludes a receiving element 108 a on the primary side and atransmitting element 108 b on the secondary side. For at least oneembodiment, the opto-coupler 108 a-b is configured to transmit to theprimary side both a wake-up signal S_(WU) and a feedback signal S_(FB).Each of these signals, which depend on mode of operation in an outputcontroller 110 (described further below), are transmitted by thesecondary side to the primary controller 102 via the opto-coupler 108a-b and the seventh primary port PP7 of the primary controller 102.Capacitor C5 provides conditioning for the received S_(WU) or S_(FB)signal. It is to be appreciated that only one of the S_(WU) or S_(FB)signal is typically transmitted from the secondary side to the primaryside at any given time by the opto-coupler 108 a-b. In accordance withat least one embodiment, a distinction between the S_(WU) and S_(FB)signals may be provided in terms of any form of analog or digital signalcharacteristic, such as voltage, current, duration, polarity, one ormore pulses, or sequences thereof, or otherwise. As discussed below, theS_(WU) signal represents a signal instructing the primary side topower-up from standby mode. S_(WU) is transmitted to the primary sidewhen a transition from standby mode to powered mode is requested by theoutput controller 110. During powered mode, the S_(FB) signalcorresponds to the output power provided by the power converter 100 tothe adaptive device 150. The primary controller 102 may use the S_(FB)signal to control the output power provided by the power converter 100to the adaptive device 150.

It is to be appreciated that other signal representations, in the analogand/or digital domains, may be used to represent and transmitinformation from an adaptive device 150 and/or the output controller 110to the primary controller 102 via one or more opto-couplers.

Primary Controller:

The primary controller 102 includes various components configured toawaken the primary side from a standby mode configuration and, duringpowered mode, to control the output voltage, and when desired, theoutput power, of the power converter 100 based on communicationsreceived from the secondary side and/or from an adaptive device 150connected to the secondary side. The components used for operationsperformed by the primary controller 102 may be provided in one or moreintegrated circuit assemblies and may include the use of commonly knowncircuit elements including, but not limited to, logical, discreteelements, active and passive elements. In accordance with at least oneembodiment, the primary controller 102 includes a primary wake-upcircuit 104 and a primary switch controller and driver circuit 106.Other components may be included in the primary controller 102, asdesired for any given implementation of one or more embodiments of thepresent disclosure. For at least one embodiment, during standby mode,the primary switch controller and driver circuit 106 is powered down.

Primary Wake-Up Circuit 104:

As shown in FIG. 1, the primary controller 102 may include a primarywake-up circuit 104 which, for at least a first embodiment, includes oneor more components configured to instruct the primary controller 102 andthe primary switch controller and driver circuit 106 to activate andbegin converting the input power received at the first port PP1 into theoutput voltages and currents desired by the adaptive device 150. Theprimary wake-up circuit 104 is suitably connected to one or more portsof the primary controller 102. The primary wake-up circuit 104 ispowered during standby mode at a minimal level necessary for it toreceive and respond to a wake-up signal received from the secondarycontroller, as described further below. It is to be appreciated that theminimal power level used will vary by implementation, but, for at leastone embodiment is less than a few milliwatts. In at least one firstembodiment, the primary wake-up circuit 104 is suitably connected to theseventh primary port PP7, via which the primary controller 102 receivesthe S_(WU) signal. Upon receipt of S_(WU), the primary wake-up circuit104 may be configured to instruct the primary switch controller anddriver circuit 106 to close the first switch S1 and begin the poweringup operations of the primary side of the power converter 100. It iscommonly appreciated that a switch mode power supply commonly undergoesa transition period during which the output power provided by the powerconverter is stabilized until a desired substantially constant outputvoltage and current is generated. During this transition period, theprimary controller 102 may be configured to begin recognizing that thesignal received at PP7 is the feedback signal S_(FB), which the primarycontroller 102 may use to adjust and control the output power of thepower converter 100.

Primary Switch Controller & Driver 106:

The primary controller 102 also may be configured to include a primaryswitch controller and driver circuit 106 configured to control theopening and closing of the first switch S1 based on signals received onthe various ports of the primary controller 102 including, but notlimited to, the feedback signal S_(FB) and, in the case of the secondembodiment of FIG. 3, the S_(PVS) signal. The operation andconfiguration of the primary switch controller and driver circuit 106may use any suitable design, such designs being well known in the art.

Secondary Side of Power Converter

Second Coil, L2:

The secondary side of the power converter 100 includes the beforementioned second coil L2 which has a fifth terminal T5 and a sixthterminal T6. As shown in FIG. 1, fifth terminal T5 is suitably connectedto diode D3 which is connected in parallel to the adaptive device 150,signal conditioning capacitor C6, and to sensing resistor R6. The secondcoil L2 generates the second current I_(S) during each duty cycle.Voltage across capacitor C6 is supplied to an output controller 110 viaa second secondary port SP2.

The sensing resistor R6 is connected in series to a cathode of diode D3and the transmitting element 108 b of the opto-coupler 108 a-b. Duringpowered mode operations, sensing resistor R6 senses the output voltageprovided by the second coil L2 to the adaptive device 150. The feedbacksignal S_(FB) is transmitted to the primary controller 102 via theopto-coupler 108 a-b. The feedback signal S_(FB) is also transmitted tothe output controller 110 via a bi-directional first secondary port SP1.

Output Controller:

The output controller 110 includes a secondary wake-up circuit 112 thatis communicatively coupled to the first secondary port SP1. The outputcontroller 110 also includes the second secondary port SP2 whichprovides power to the output controller 110. During powered mode, thepower is provided by the voltage and current induced by transformer 101in the second coil L2. During standby mode and upon the receipt of arequest by a device 150 for power from the power converter, power to theoutput controller 110 is provided by battery 156 in the adaptive device150 via the circuit formed with the closing of device switch SD. Asdiscussed below, when a transition is requested from standby mode topowered mode, the device 150 is configured to close switch SD, uponwhich an electrical circuit is configured between battery 156 and outputcontroller 110.

The output controller 110 also includes a third secondary port SP3 thatcan be communicatively coupled to device 150 such that one or moreinstructions may be communicated by device 150 to output controller 110.In at least one embodiment, secondary port SP3 is a bi-directional portfacilitating the communication of information signals by and betweenpower converter 100 and device 150. In at least another embodiment,secondary port SP3 is unidirectional and supports the communication ofinformation signals from device 150 to power converter 100. Thirdsecondary port SP3 may receive, from device 150, a device wake-up signalS_(DWU). S_(DWU) may be used to instruct power converter 100 totransition from standby mode to powered mode. S_(DWU) may be generatedby device 150 upon establishment of an electrical connection betweendevice 150 and power converter 100, or at any time thereafter. Inaccordance with at least one embodiment, device 150 may be configured toperiodically send S_(DWU) to power converter 100 to maintain a trickleor other charge on battery 156. During such periodic charging, powerconverter 100 may be configured to transition from standby to powered tostandby mode repeatedly and thereby minimize energy use during periodswhen the device 150 is not otherwise needing power from the powerconverter 100.

Referring now to FIG. 2, one embodiment of a method for transitioning apower converter from standby mode to powered mode is shown. PerOperation 200, this method begins when power converter 100 entersstandby mode and continues while the converter remains in standby mode.As discussed above, power converter 100 may enter standby mode basedupon any of many events. For example, when device 150 is disconnectedfrom power converter 100, the drop in the secondary current I_(S), willbe reflected by a corresponding change in the primary current I_(P),with such change being detectable via the third coil L3, and representedin either of the applied voltage signal S_(VDD) or the scaled primaryvoltage signal S_(PVS). It is to be appreciated, that in certainembodiments the change in I_(P) may be more readily detectable using thescaled primary voltage signal S_(PVS). Similarly, operation 200 occurswhen the load requested by a device 150 is zero for one or more dutycycles. As discussed above, a device 150 may be configured to determinewhen it is fully charged but remains connected to power converter 100.Upon determination of such a state, the device 150 may be configured toopen switch SD, which opens the circuit between battery 156 and powerconverter 100. Upon opening switch SD, the secondary current I_(S) willfall rapidly, while the output voltage is maintained at a constantvoltage by the power converter 100. Additionally, device 150 may beconfigured to communicate to output controller 110 an inverse of theS_(DWU) signal, such inverse signal may be represented in an analog ordigital format and may be configured to instruct the power converter 100to enter standby mode.

In Operation 202, the process continues with a determination of whethera device is connected. It is to be appreciated, that in accordance withat least one embodiment where standby mode is entered when device 150 isdisconnected and the transformer 101 shortly thereafter is no longerinducing voltages and currents in the second coil L2, operations 200 and202 are conducted after device 150 is connected to the power converter100. For such a scenario, the output controller 110 is typicallyunpowered until a device is again connected to the power converter. Whena device 150 is again connected to the power converter 100, thearbitrary device voltage potential V_(DP) at the third secondary portSP3 may be detected corresponding to the ratio between R_(D) and R7 of avoltage divider circuit. That is, via the V_(DP) signal, power converter100 may determine whether device 150 is connected even when deviceswitch SD is open. It is to be appreciated that the voltage changesneeded by the output controller 110 to detect a change in the V_(DP)signal representing the attaching of device 150 to the power converter100 may be less than a few milliwatts.

In Operation 204, the transition from standby mode to powered mode mayoccur with the closing of the device switch SD. By closing SD, battery156 provides power to output controller 110 via the second secondaryport SP2 (as per Operation 206).

Per Operation 206, the output controller 110 is now powered by thebattery 156. During this state and for at least one embodiment, theoutput controller 110 may be configured to prevent the powering of thetransmitting element of the opto-coupler 108 b by not grounding thefirst secondary port SP1. While not shown in FIG. 1, it is to beappreciated that for at least one embodiment, the secondary wake-upcircuit 112 may be configured to control the flow of electrical currentsthrough the first secondary port SP1 and, thereby, thru the transmittingelement of the opto-coupler 108 b. For one such configuration, currentmay be allowed to flow through the transmitting side of the opto-coupler108 b after receipt of a device wake-up signal S_(DWU) via the thirdsecondary port SP3 of the output controller 110 (per Operation 208). Itis to be appreciated that such an embodiment may configure the powerconverter 100 for transitioning from standby mode to powered mode tooccur after the output controller 110 has been powered or has otherwisereached a stable operating state. In other embodiments, the secondarywake-up circuit 112 may be configured to automatically close a circuitconnected to the transmitting element of the opto-coupler 108 b suchthat upon closing of the device switch SD, the transmitting side 108 bcommunicates the S_(WU) signal to the receiving side 108 a of theopto-coupler without requiring the device 150 to separately send thedevice wake-up signal S_(DWU).

In another embodiment, the device 150 may be configured to include asignaling circuit 152 and a detecting circuit 154. The detecting circuit154 may be configured to detect the connection between the powerconverter 100 and device 150. When connecting the power converter 100 todevice 150, the signaling circuit 152 may be configured to close thedevice switch SD to power the output controller 110 so that a transitionfrom standby mode to powered mode may occur in the output controller110. Per at least one embodiment, the device switch SD may betemporarily closed, as instructed by signaling circuit 152, such that anelectrical signal of sufficient time and duration is provided thatawakens the output controller 110. Upon closing of the device switch SD,the signaling circuit 152 may be configured to then send the devicewake-up signal S_(DWU) to the output controller 110 via the thirdsecondary port SP3 (Operation 207). The device wake-up signal S_(DWU)may then be provided to the secondary wake-up circuit 112, whichactivates the transmitting element of the opto-coupler 108 b and therebycommunicates the wake-up signal S_(WU) to the primary side of the powerconverter 100. Accordingly, in FIG. 1, the wake-up signal S_(WU) isshown to be bi-directional, although it is to be appreciated that it istypically used with only one direction of current flow, as per a givenimplementation of the one or more described embodiments.

As discussed above and as represented by Operation 208, the wake-upsignal S_(WU) is transmitted to the primary controller 102. As perOperation 210, the wake-up signal S_(WU) is received by the primarycontroller by the receiving element of the opto-coupler 108 a. Next, perOperation 212, the primary controller 102 is awoken and automaticallybegins stabilizing its operations for powered mode. As per Operation214, after transitioning from standby mode to powered mode, the supplyvoltage signal S_(VDD) will increase to voltage level to operate theprimary controller 102 via input voltage of the first port PP1, resistorR1 and the second primary port PP2. After the primary controller isoperated by the increase of the supply voltage signal S_(VDD), the powerconverter 100 starts to provide the power to the device 150 under theclosing of the device switch SD. In another embodiment, upon opening ofthe device switch SD after receipt of a device wake-up signal S_(DWU)via the third secondary port SP3 of the output controller 110 (perOperation 208), the output voltage V_(DD) that the power converter 100may provide to the device 150 will also increase. In at least oneembodiment, these increases in V_(DD) may be communicated by the outputcontroller 110 to the device 150 via the third secondary port SP3. Uponthe output voltage V_(DD) reaching a desired threshold, the device 150may be configured to again close the device switch SD and thereby powerthe device and/or charge the battery 156 using the power provided by thepower converter 100. In another embodiment, the device 150 may beconfigured to close the device switch SD after a given amount of timehas elapsed since the device wake-up signal S_(DWU) was sent by thedevice 150 to the power converter 100.

In operation 216, the primary controller 102 is operated according tosteady-state parameters and provides electrical power to the device 150until the next transition to standby mode occurs.

Output Switch Controlled Power Converter Embodiment

In FIG. 3, a second embodiment of a power converter 300 is shown. Forthis embodiment, the secondary side includes a second switch S2 that maybe used to control the duty cycle for the second coil L2 (herein, the“second duty cycle”). In FIG. 3, elements common to the embodimentsdescribed with respect to FIG. 1 are configured and operate the same,unless otherwise further described herein.

As shown in FIG. 3, primary controller 102-B includes a primary switchcontroller and driver 106 and a primary powered coil wake-up circuit302. Primary controller 102-B is configured to receive the S_(V),S_(PV), S_(VDD), S_(PVS), and S_(FB) signals and send the S_(PG) signalvia ports PP1-PP7. Primary powered coil wake-up circuit 302 differs fromthe primary wake-up circuit 104 in that it is not configured to receiveor awaken the primary controller 102 upon receipt of a wake-up signalS_(WU) sent by the output controller 110 via the opto-coupler 108 a-bfor the embodiment of FIG. 1. Instead, per the embodiment of FIG. 3, theopto-coupler 108 a-b is not used to send a wake-up signal S_(WU) to theprimary controller 102.

Upon the generation of a scaled primary voltage signal S_(PVS) by thethird coil L3, due to the powering of the second coil L2 by the battery156 of the device 150, the primary powered coil wake-up circuit 302detects the scaled primary voltage signal S_(PVS) induced in the thirdcoil L3 and activates the primary controller 102-B. It is to beappreciated that either the applied voltage signal S_(VDD) or the scaledprimary voltage signal S_(PVS), with the latter providing greatersensitivity but less power to the primary controller 102-B, may beutilized to signal the primary powered coil wake-up circuit 302 totransition the primary controller 102-B from standby mode to poweredmode. It is to be appreciated that using voltage induced in the thirdcoil L3 from the second coil L2 by the battery 156, the primarycontroller 102-B may be configured to detect and interpret as a requestby the device 150 to transition from standby mode to powered mode.

As further shown in FIG. 3, the second coil L2 is connected via thesixth terminal T6 to a secondary switch S2. In at least one embodiment,the secondary switch S2 is a MOSFET with the drain being connected tothe sixth terminal T6. It is to be appreciated that in otherembodiments, other configurations and or arrangements of switchingcomponents, including MOSFETS or otherwise, may be utilized as desiredfor any implementation. A diode D5 represents the body diode of MOSFETS2. The drain of the secondary switch S2 is connected to sixth terminalT6, the source is connected to ground, and the gate is connected to asecond output controller 304 via a fourth secondary port SP4.

During powered mode of operation, the conduction loss of diode D5 may bereduced by controlling the second duty cycle. The second duty cycle maybe controlled by the second output controller 304 via a secondary gatesignal S_(SG). More specifically and per at least one embodiment of thepresent disclosure, a secondary switch controller 306 is communicativelycoupled, via the second secondary port SP2 to the gate of the secondswitch S2. The secondary switch controller 306 generates the secondarygate signal S_(SG), which is used to control the second duty cycle andthereby the reduced conduction loss of the power converter 300 duringpowered mode. Secondary switch S2 may be used in one or more embodimentsto reduce conduction losses, as desired for any given implementation.

The secondary switch controller 306 may also be used during standby modeto signal the primary controller 102-B that a transition from standbymode to powered mode has been requested by the device 150. As discussedabove, for at least one embodiment, by controlling the status(open/closed) of the device switch SD and the second switch S2, acircuit may be formed by which the battery 156 of the device 150generates voltage across the second coil L2, which induces voltageacross in the third coil L3. The primary powered coil wake-up circuit302 may be configured to determine that a transition is desired from astandby mode to a powered mode based upon the generation of such voltageacross the third coil L3. This voltage may be represented in one or moreof the applied voltage signals S_(VDD) and the scaled primary voltagesignal S_(PVS).

The second output controller 304 may be configured to generate thesecond gate signal S_(SG) upon receipt of the device wake-up signalS_(DWU), upon receipt of an output voltage V_(DD) generated by thebattery, for example, upon the closing of device switch SD, orotherwise.

In FIG. 4, a method for using the second power converter 300 to controltransitions from standby mode to powered mode is shown. The methodincludes Operations 200, 202, 204, 206, and 207 which proceed asdiscussed above. Per Operation 400, upon receipt of the device wake-upsignal S_(DWU) the secondary switch controller 306 closes the secondswitch S2, thereby applying voltage of the battery 156 across the secondcoil L2. As discussed above, this voltage induces corresponding voltageacross the third coil L3, which generates the applied voltage S_(VDD)and the scaled primary voltage S_(PVS) signals used to awaken theprimary controller. The transition to powered mode then continues withoperations 212, 214, and 216 as discussed above.

Compensated Power Converter Embodiment

Referring now to FIG. 5, a third power converter 500 configured totransition from standby mode to powered mode is shown, wherein theprimary side of the power converter remains powered during standby modeoperations. Per this embodiment, during standby mode the primarycontroller 102 controls the primary side of the power converter 500 suchthat the no-load output voltage is maintained between 3-7 volts, forexample. It is to be appreciated, that such a mode of operation mayresult in large output ripples being generated in the output voltagewhen a device 150 is disconnected from the power converter 500. Tocontrol such ripples and other dynamic characteristics of the powerconverter when in standby mode, a third output controller 510 isconfigured to slowly respond to such fluctuations in the output voltage.As shown, the third power converter 500 may be configured to include avoltage divider circuit including resistors R8 and R9 that generate areference voltage signal V_(REF). V_(REF) is provided, via a fifthsecondary port SP5, to a compensator circuit 502 provided in a thirdoutput controller 510. The compensator circuit 502 may be configured todetect and control fluctuations in the output voltage using any desiredtechnique or approach.

Further, for at least one embodiment, the device wake-up signal S_(DWU)may be utilized to instruct the power converter 500 to transition topowered mode. Such transition occurs as discussed above with respect tothe first embodiment and the first flow, with the exception that thethird output controller 510 does not utilize power from the battery 156to perform the transition. Instead, the third output controller 510remains powered by the currents induced in the second coil L2 by theprimary coil L1. It is to be appreciated that the faster compensator 600is configured to respond to ripples in the output voltage, V_(DD)generally increases standby power correspondingly. Contrarily, if theresponse of the compensator 600 is slow, standby power may be reduced,but output ripples and other undesired characteristics in the outputvoltage may be generated.

Given these concerns, in FIG. 6, one embodiment is shown of acompensator circuit 600 which can automatically adjust to fluctuationsin the output voltage to achieve a desired response. The compensatorcircuit 600 may be provided in a third power converter 500 configured toreceive and send, as discussed above, the S_(DWU), V_(DP), V_(REF),V_(DD), S_(FB), and S_(WU) signals (for purposes of simplifying thisdescription, all ports and signals received and/or sent by third outputcontroller 510 are not shown in FIG. 6). The compensator circuit 600 mayinclude a amplifier 602 configured to receive the V_(REF) signal,compare such signal to a set threshold as specified by the voltage ofcapacitor C7, and output a compared reference voltage. Voltage ofcapacitor C7 may be set based upon observed responses of the powerconverter to a range of output voltages, based on mathematical analysisor otherwise. Compensator circuit 600 also includes an attachmentdetector 604 configured to receive the V_(DP) signal which, as discussedabove can be used to detect the attachment of a device to the powerconverter. The attachment detector 604 is configured to control theresistance of resistor R10 based upon whether a device is or is notattached to the power converter. Per at least one embodiment, theresistance of resistor R10 is decreased when a device is attached andthe resistance is increased when a device is detached. These changes inresistance are communicated in the feedback signal S_(FB) which theprimary controller 102 may utilize to control the operation of the firstswitch S1 and, thereby, the power converter during standby mode toutilize as little power as necessary.

Per at least one embodiment, the compensator 600 may be configured suchthat before a device is attached to the power converter, the resistanceR10 is set very large and the response of the compensator to changes inthe output voltage, as represented by V_(REF), may be very slow. It isto be appreciated, that the larger the resistance R10 utilized, the lesspower is wasted during standby mode. After a device is attached, asdetected for at least one embodiment by a change in the V_(DP) signal,the resistance may be set to very small, with a very fast response. Itis to be appreciated that other permutations of resistances may beutilized to tune a power converter to provide a given response rate inview of power consumed during standby mode operations.

Controlled Minimum Primary Current Embodiment

In FIG. 7, a fourth embodiment 700 of a power converter configured tominimize power losses during standby mode and automatically transitionfrom standby mode to powered mode is shown. Per this embodiment and likeone or more of the embodiments described above, such as by example theembodiment of FIG. 5, during standby mode the primary controller mayremain powered and the output voltage may be maintained between adesired range. It is to be appreciated, however, that during standbymode occasional activations of the primary coil, by controlling thestatus of the first switch, may be used to maintain the output voltagebetween the desired range. Per at least the embodiment of FIG. 7, theseoperations and transitions between standby and powered modes may befurther controlled by use of an I_(MIN) controller 702, which for atleast one embodiment is configured for use on the primary side of thepower converter 700.

More specifically, as shown in FIG. 8, primary controller 102 may beconfigured to include an I_(MIN) controller circuit 800. For at leastone embodiment, the I_(MIN) controller 800 may be connected to receivethe S_(FB) and S_(VDD) signals and output a modified feedback signalS_(FBM) to one or more primary switch controller and driver 106components that are commonly utilized to control the operation of thefirst switch. The I_(MIN) controller 800 is powered by S_(VDD), which asdiscussed above can be generated by the third coil L3, and is connectedto resistor R10, which has a fixed impedance of Z_(FB). For at least oneembodiment, the impedance of resistor R10 may be adjustable, as may bedesired, for example, when a power converter is configured to providevariable output voltages, versus a fixed output voltage. An embodimentof a power converter so configured is described in U.S. patentapplication Ser. No. 15/683,939, filed on Aug. 23, 2017, the entirecontents of which are incorporated herein by reference.

The I_(MIN) controller 800 may also be configured to include diode D6having an anode connected in parallel with port PP7 and resistor R10 anda cathode connected in series with a voltage divider circuit formed byresistors R11 and R12. The impedance values of resistors R11 and R12 areselected to scale the received feedback signal S_(FB), as adjusted basedon the output voltage of resistor R10, to generate a scaled feedbacksignal S_(FBS) for input to a low voltage dominant bypass circuit 802.

The low voltage dominant bypass circuit 802 is configured to alsoreceive a current limit signal V_(CS-LIM). The current limit signal maybe used to protect components from excessive currents by providing ahigh threshold limit which the pulse-by-pulse peaks of the primarycurrent I_(P) do not exceed. The low voltage dominant bypass circuit 802outputs the lesser of the S_(FBS) and V_(CS-LIM) signals to a highvoltage dominant bypass circuit 804.

The high voltage dominant bypass circuit 804 is also configured toreceive a V_(IMIN1) or a V_(IMIN2) signal from selector 812 and comparesuch received signal with the low voltage dominant bypass output signalS_(LD). The high voltage dominant bypass circuit 804 output the higherof the low voltage dominant bypass output signal SLD and the signalreceived from selector 812. In this manner, the power converter 700 maybe configured to provide over-current protection for itself and anyconnected device during all modes of operation including powered,standby and transitions therebetween.

For at least one embodiment, selector 812 may be configured to selecteither the V_(IMIN1) threshold or the V_(IMIN2) threshold based on thelast received feedback signal S_(FB). More specifically, when a deviceis attached to the power converter 700 the feedback signal S_(FB) willchange rapidly, for example become high fast, due to some amount ofcurrent being loaded. Selector 812 may be configured to detect thesechanges and switch from the V_(IMIN2) threshold to the V_(IMIN1)threshold, which respectively represent the desired levels in theprimary current I_(P) during time periods t1 to t3, as shown in FIGS. 9Aand 9B, where V_(IMIN1) is used when a device is attached and V_(IMIN2)is used when a device is not attached. The values of V_(IMIN1) andV_(IMIN2) for any given embodiment can be selected based uponmathematical analysis, experimental results, or otherwise.

As further shown in FIG. 9A for when a device is attached, the feedbacksignal S_(FB) oscillates repeatedly over time in accordance withstandard power converter operations over one or more powered switchingcycles, as shown arising from t₀ to t₄. Over each such switching cycle,a nominal ripple, S_(VDD (Ripple-Powered)) will typically occur in theapplied voltage signal S_(VDD).

As further shown in FIG. 9B for when a device is not attached, theswitching cycle is extended, as shown for a standby switching cycle nowarising from t₀ to 2t₀. This results in a larger standby rippleS_(VDD (Ripple-Standby)) arising during which the power converter usesless power than is used during powered mode. It is to be appreciatedthat the resulting applied voltage signal for standby mode is less thanfor powered mode, which are respectively shown in FIGS. 9B and 9A by therespective S_(VDD (nominal standby)) and S_(VDD (nominal powered))values.

As further shown in FIG. 8, the IMIN controller circuit 800 may beconnected, for at least one embodiment, to a comparator 808 of a primaryswitch controller circuit 806. The comparator 808 may also be connecteda leading-edge blanking circuit 810 and a switch driver 814. The switchdriver 814 may be connected to an oscillator 812 and transmits theprimary gate signal S_(PG) during each switching cycle in accordancewith at least the principles of operations shown in FIGS. 9A and 9Band/or as discussed otherwise herein. The principles of operation of thecomponents of the primary switch controller circuit 806 are well knownin the art.

Although various embodiments of the claimed invention have beendescribed above with a certain degree of particularity, or withreference to one or more individual embodiments, those skilled in theart could make numerous alterations to the disclosed embodiments withoutdeparting from the spirit or scope of the claimed invention. Thecomponents used and described herein may be provided in one or moreintegrated circuit assemblies and may include the use of commonly knowncircuit elements including, but not limited to, logical, discreteelements, active and passive elements. Other embodiments are thereforecontemplated. It is intended that all matter contained in the abovedescription and shown in the accompanying drawings shall be interpretedas illustrative only of embodiments and not limiting. References tofirst, second, etc. terminals, coils, components or otherwise are forpurposes of explanation and clarity only and are not intended to belimiting. Changes in detail or structure may be made without departingfrom the basic elements of the invention as defined in the followingclaims.

What is claimed is:
 1. A device, comprising: an output controller havinga third secondary port; wherein the output controller is configured tomonitor a voltage potential at the third secondary port; and wherein thethird secondary port is electrically grounded via a first resistance;and wherein, when an adaptive device is coupled to the output controllervia the third secondary port, a voltage divider circuit is formed by anadaptive device resistance and the first resistance; wherein the outputcontroller is configured to detect a change in the voltage potential atthe third secondary port when the voltage divider circuit is formed. 2.The device of claim 1, wherein the output controller further comprises:a second secondary port electrically coupled to a second coil of a powerconverter.
 3. The device of claim 2, wherein the second coil provideselectrical power to the output controller and the adaptive device whenthe power converter is in a powered mode; and wherein an adaptive devicebattery provides power to the output controller while the powerconverter transitions from a standby mode to the powered mode.
 4. Thedevice of claim 2, wherein the output controller is configured toreceive a device wake-up signal.
 5. The device of claim 4, wherein thedevice wake-up signal is received at the third secondary port.
 6. Thedevice of claim 5, wherein the output controller further comprises asecond secondary port; wherein the adaptive device resistance arisesbetween a device signaling circuit and the third secondary port; whereinthe device wake-up signal is output by the device signaling circuit; andwherein the output controller is configured to receive electrical powerfrom an adaptive device battery when the adaptive device battery iselectrically coupled to the second secondary port.
 7. The device ofclaim 6, wherein, to initiate a transition of the power converter from astandby mode to a power mode of operation, the adaptive device connectsthe adaptive device battery to the second secondary port.
 8. The deviceof claim 2, wherein the output controller is configured to receive adevice wake-up signal from the adaptive device at the third secondaryport; wherein upon receiving the device wake-up signal, the outputcontroller is configured to initiate transition mode during which thepower converter transitions from a standby mode to a powered mode;wherein during standby mode, the output controller is unpowered; whereinduring transition mode, the output controller receives electrical powerfrom an adaptive device battery; and wherein during powered mode, theoutput controller receives electrical power from the second coil.
 9. Thedevice of claim 8, wherein the output controller further comprises: afirst secondary port electrically coupled to a data coupling device; andwherein the output controller is configured to selectively operate thetransmitting side of the opto-coupler during transition mode.
 10. Thedevice of claim 8, wherein the power converter further comprises aprimary controller communicatively coupled to the output controller viaan opto-coupler having a transmitting side and a receiving side; andwherein, during the transition mode, the output controller is configuredto selectively ground the transmitting side of the opto-coupler tocommunicate a request to the primary controller.
 11. The device of claim10, wherein the output controller further comprises: a wake-up circuitconfigured to perform at least one of the operations of: monitoring thevoltage potential at the third secondary port; detecting a change in thevoltage potential at the third secondary port; and selectively groundingthe transmitting side of the opto-coupler.
 12. The device of claim 11,wherein, during the powered mode, the opto-coupler is configured tocommunicate a feedback signal to the primary controller.
 13. A secondarycontroller for a power converter, comprising: a first secondary port; asecond secondary port; and a third secondary port; wherein the secondarycontroller is configured for use of the first secondary port tocommunicate at least one signal to a primary controller of the powerconverter; wherein the secondary controller is configured to receiveelectrical power via the second secondary port; and wherein thesecondary controller is configured to detect a change in voltagepotential arising when an adaptive device is connected to the powerconverter.
 14. The secondary controller for a power converter of claim13, wherein the at least one signal communicated via the first secondaryport includes at least one of a wake-up signal and a feedback signal;and wherein the wake-up signal is communicated upon the secondarycontroller receiving a device wake-up signal from the adaptive device.15. The secondary controller for a power converter of claim 14, whereinthe device wake-up signal is received at the third secondary port whilethe second secondary port is electrically connected to and receiveselectrical power from an adaptive device battery.
 16. The secondarycontroller for a power converter of claim 15, further comprising: awake-up circuit, coupled to the third secondary port; wherein thewake-up circuit is configured to detect the change in voltage potential,when the device is coupled to the output controller via the thirdsecondary port, using a voltage divider circuit formed by an adaptivedevice resistance and a first resistance.
 17. A method for operating apower converter, comprising: during a powered mode of operation,receiving electrical power, by a secondary controller for a powerconverter, from a second coil of a transformer in the power converter;during a standby mode of operation, powering down the secondarycontroller; and monitoring a voltage potential at a port of thesecondary controller; and initiating a transition mode of operation by,detecting a change in the voltage potential; wherein the change involtage potential occurs when an adaptive device and the secondarycontroller form a voltage divider circuit that changes the voltagepotential.
 18. The method of operating a power converter of claim 17,comprising: during the transition mode of operation, receivingelectrical power, by the secondary controller, from an adaptive devicebattery; receiving, by the secondary controller, a device wake-up signalfrom the adaptive device; and in response to the device wake-up signal,communicating a request by the secondary controller to a primarycontroller.
 19. The method of operating a power converter of claim 18,wherein communicating the request by the secondary controller to theprimary controller comprises: selectively grounding, by the secondarycontroller, a transmit side of an opto-coupler; wherein the transmitside of the opto-coupler is electrically coupled to the secondarycontroller and a receive side of the opto-coupler is electricallycoupled to the primary controller.
 20. The method of operating a powerconverter of claim 19, further comprising: during transition mode,stabilizing operation of the power converter until an applied voltagesignal received in a feedback signal communicated by the secondarycontroller to the primary controller via the opto-coupler increases to adesired voltage level; wherein powered mode occurs upon the appliedvoltage signal reaching the desired voltage level; and during poweredmode, providing an output power by the power converter to the adaptivedevice.